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PubMedDate not supplied

[The discrimination of color images in human operative memory].

Qualitative changes of color image maintained in the operative memory were studied using the modified Sperling's strategy. On the basis of estimations of difference between any two color images (from nine possible), contained in the same memory volume within 50 and 100 ms, the respective mnemonic spaces were built and afterwards correlated with the perceptual and semantic spaces. It was found out that the maintenance of a color image in the operative memory was affected by two simultaneous but independent factors. The first factor described the fading, i.e., extent of the intensity loss of the primary color image in the process of its maintenance in the operative memory. Fading was accompanied by a decrease in the signal-to-noise ratio and increase in the incidence of the casual mistakes in comparing the images with each other. The second factor determined the systematic transformation of color images in the memory expressed in the effect of clusterization of point stimuli and specific change in the between-point distances (estimations of difference).

Adolescent↗
PubMed1990

Psychology of office design.

The design of a physician's office can affect whether patients return, follow advice, or recommend the physician to other people. Color is an important element in design. It can make people relaxed or excited; it can help or hinder vision. Decreased color perception and differentiation occurs with increased age. In addition, color reflects the personality of the person who chooses or uses it. Furniture also reflects personality. Arrangement is important in making people feel comfortable and easy and safe to move between pieces. Most people prefer to sit alone when waiting to see physicians. Firm-cushioned furniture with arm rests allows people to sit and rise more easily. Color, mirrors, glass, and other decorating items can help make a small space look larger, a narrow space wider, or a low space higher. Mixing textures creates interesting effects. Patterns in wall coverings and upholstery also increase visual interest and alter perception of size and shape. Personal mementos can make patients feel a physician is a more humane person, although they also can make a female physician appear less professional and capable, depending on the patients' perceptions. Even lighting levels increase visual acuity. People usually prefer some closeness in architecture as a defensive position. Institutionalized approaches to building increase patients' anxiety. The reception area makes the first impression. It should be welcoming, restful and divided into smaller waiting areas. Incandescent lighting is more relaxing than fluorescent.(ABSTRACT TRUNCATED AT 250 WORDS)

Facility Design and Construction↗
PubMed2003

The influence of color on the perception of luminance motion.

We examined the role of color in the processing of motion of a luminance-varying pattern by alternating the color of a moving pattern and measuring the luminance contrast required for accurate discrimination of the motion direction. We report that the contrast threshold for perceiving the direction of motion of luminance-varying patterns is greatly elevated when the mean chromaticity of the moving luminance pattern alternates between two hues. Thus, color plays a critical role in the discrimination of luminance motion direction. The magnitude of the threshold elevation is directly related to the magnitude of the LM opponent color contrast produced by the color alternation. S-cone contrast produces little or no effect. The interference produced by color alternation was greatly reduced in the retinal periphery. Our results indicate that first-order luminance motion mechanisms are sensitive to the color of moving objects as coded by a differencing of the outputs of L and M cones. Contrary to the widely accepted notion that luminance-defined motion is processed primarily in the spectrally broadband magnocellular (M) pathway, our results suggest that the hue-selective parvocellular (P) mechanisms provide input to first-order motion detectors.

Color Perception↗
PubMed2005

Comparison of in vivo visual and computer-aided tooth shade determination.

The aim of this study was to evaluate the performance of shade-determining devices. For the daily practitioner, it is essential to know whether modern computer-aided shade selection is reliable in everyday life. So the question of how the clinical usability of these machines could be rated has to be clarified. In the following, three actual devices available in the market were compared using a human observer's perception. The SpectroShade device (MHT Optic Research AG, 8155 Niederhasli, Switzerland), the ShadeVision device (X-Rite Co., Grandville, USA) and the Digital Shade Guide DSG4 (A. Rieth, 73614 Schorndorf, Germany) were assessed with respect to their agreement with the color perception of three examiners looking at 57 test persons (six teeth each for a total of 342). Shades were reported in Vita Classical shades. It could be demonstrated that every single human examiner showed a significantly higher agreement value (human group on average 40.2%) when compared with the remaining five methods than each computer-aided tooth shade determination device. The devices reached on average only a value of 28.6%, whereas the X-Rite ShadeVision showed a significant better result (33.2%) than the MHT SpectroShade and Rieth DSG4 (27.0 and 25.7%). Identical shade results given by all three methods of a group (group of three devices and three humans) were found to be rather low for the computer-aided devices (9.9%) compared with humans (36.7%). All six methods together agreed in 3.3% of the cases. It becomes evident that the methods-especially the computer-aided shade determination-are rather divided about the respective tooth color. Deficiencies of the instrumental as well as the visual detection become obvious. The best agreement level was performed by the human examiners. The best agreement of the evaluated devices was obtained-generally as well as among the human testers-by the X-Rite ShadeVision system, followed at a statistically significant distance by the MHT SpectroShade and the Rieth DSG4. The agreement among the examiner group was 52.9%, significantly better than that of each device compared to this group (31.3% on average). Color detection and its realization are very complex. As shown, in many cases, computer-aided color shade determination of natural teeth seems to not reflect human perception.

Adult↗
PubMed1987

Psychophysical evidence for separate channels for the perception of form, color, movement, and depth.

Physiological and anatomical findings in the primate visual system, as well as clinical evidence in humans, suggest that different components of visual information processing are segregated into largely independent parallel pathways. Such a segregation leads to certain predictions about human vision. In this paper we describe psychophysical experiments on the interactions of color, form, depth, and movement in human perception, and we attempt to correlate these aspects of visual perception with the different subdivisions of the visual system.

Color Perception↗
PubMed2005

Cone cGMP-gated channel mutations and clinical findings in patients with achromatopsia, macular degeneration, and other hereditary cone diseases.

Unrelated patients with achromatopsia, macular degeneration with onset under age 50 years, cone degeneration or dysfunction, cone-rod degeneration, or macular malfunction were screened for mutations in the three genes known to be associated with achromatopsia: the GNAT2 gene encoding the alpha subunit of cone transducin and the CNGA3 and CNGB3 genes encoding the alpha and beta subunits of the cone cGMP-gated cation channel. We found no examples of patients with GNAT2 mutations. Out of 36 achromats, 12 (33%) had mutations in CNGA3 (13 different mutations including five novel mutations) and 12 (33%) had mutations in CNGB3 (six different mutations including four novel mutations). All achromats with CNG mutations had residual, presumably cone function as determined by computer-averaged 30-Hz electroretinograms (ERGs). There was considerable variability in acuity and color vision, with most patients having acuities of 20/200-20/400 and complete absence of color perception, and others having acuities of 20/25-20/40 and some color vision. Two pseudodominant achromatopsia cases were uncovered, both with CNGA3 mutations, including one family in which some compound heterozygotes with achromatopsia mutations were clinically unaffected. We found two novel CNGB3 changes in three patients with juvenile macular degeneration, a phenotype not previously associated with mutations in the cone channel subunits. These patients had subnormal acuity (20/30-20/60), normal to subnormal color vision, and normal to subnormal full-field cone ERG amplitudes. Our results indicate that some patients with channel protein mutations retain residual foveal cone function. Based on our findings, CNGB3 should be considered as a candidate gene to be evaluated in patients with forms of cone dysfunction, including macular degeneration.

Adult↗
PubMed1995

Color changes in dry-pigmented maxillofacial elastomer resulting from ultraviolet light exposure.

Five dry pigments and one maxillofacial elastomer were evaluated for color changes (delta E) resulting from prolonged exposure to two types of ultraviolet light. The elastomer, pigments, and pigmented elastomers were subjected to each ultraviolet light source for 400, 600, and 1800 hours, and delta E color shifts were determined. The unpigmented elastomer underwent minimally perceptible color change after 600 hours of exposure to both types of ultraviolet light. Two pigments underwent substantial color change after 400 hours, whereas the remaining three pigments remained color stable after 1800 hours. It was concluded that for the materials tested, early color changes in a prosthesis may be the result of degradation of certain ultraviolet light-susceptible pigments, whereas longer term color shifts may be caused by color changes within the elastomer.

Analysis of Variance↗
PubMedDate not supplied

Color vision testing.

1. Color deficiency occurs in about 8% of the population, due to alterations in the chemistry of one of the three receptive pigments for colored light, or the substitution of one pigment for another in the photoreceptor cones. 2. Subjects with pigment alteration can see a broad range of color; those with substitution of one pigment for another have broad areas of color perception defect. 3. The most common tests are pseudoisochromatic (color confusion) plates, designed with patterns hidden to the color deficient. Other tests use colored caps, tracing patterns, or an anomaloscope.

Color Vision Defects↗
PubMedDate not supplied

Color stability of resin cements after accelerated aging.

The color stability of both light- and dual-polymerized samples of three shades of three commercial resin cements was measured using a reflection spectrophotometer after accelerated aging over a period of 179 hours. Porcelite cement was the most color stable, followed by Optec and then 3M. The Optec and Porcelite cements changed color after accelerated aging, but with one exception the changes were not perceptible. Five of six 3M cements had perceptible color changes after accelerated aging, becoming darker and more yellow. The two lighter shades of Optec and 3M changed color more than the darker shade. Most differences between light- and dual-polymerized samples were significant but none was perceptible.

Analysis of Variance↗
PubMed2000

Hypnotic visual illusion alters color processing in the brain.

OBJECTIVE: This study was designed to determine whether hypnosis can modulate color perception. Such evidence would provide insight into the nature of hypnosis and its underlying mechanisms. METHOD: Eight highly hypnotizable subjects were asked to see a color pattern in color, a similar gray-scale pattern in color, the color pattern as gray scale, and the gray-scale pattern as gray scale during positron emission tomography scanning by means of [(15)O]CO(2). The classic color area in the fusiform or lingual region of the brain was first identified by analyzing the results when subjects were asked to perceive color as color versus when they were asked to perceive gray scale as gray scale. RESULTS: When subjects were hypnotized, color areas of the left and right hemispheres were activated when they were asked to perceive color, whether they were actually shown the color or the gray-scale stimulus. These brain regions had decreased activation when subjects were told to see gray scale, whether they were actually shown the color or gray-scale stimuli. These results were obtained only during hypnosis in the left hemisphere, whereas blood flow changes reflected instructions to perceive color versus gray scale in the right hemisphere, whether or not subjects had been hypnotized. CONCLUSIONS: Among highly hypnotizable subjects, observed changes in subjective experience achieved during hypnosis were reflected by changes in brain function similar to those that occur in perception. These findings support the claim that hypnosis is a psychological state with distinct neural correlates and is not just the result of adopting a role.

Adult↗
PubMed1993

Functional segregation of color and motion perception examined in motion nulling.

We examine two hypotheses about the functional segregation of color and motion perception, using a motion nulling task. The most common interpretation of functional segregation, that motion perception depends only on one of the three dimensions of color, is rejected. We propose and test an alternative formulation of functional segregation: that motion perception depends on a univariate motion signal driven by all three color dimensions, and that the motion signal is determined by the product of the stimulus contrast and a term that depends only on the relative cone excitations. Two predictions of this model are confirmed. First, motion nulling is transitive: when two stimuli null a third they also null another. Second, motion nulling is homogeneous: if two stimuli null one another, they continue to null one another when their contrasts are scaled equally. We describe how to apply our formulation of functional segregation to other behavioral and physiological measurements.

Color Perception↗
PubMed1995

Color stability of light-cured and post-cured composites.

PURPOSE: To determine the color stability of five composites after light-curing and recommended post-curing using reflection spectrophotometry. MATERIALS AND METHODS: Samples of the composites were prepared as disks 10 mm in diameter and 1 mm thick. The pre-cured samples were prepared with a clear plastic sheet on the top and bottom of disk, pressed between two glass slabs to the thickness of the mold, and then removed from between the glass slabs. The color of the samples was measured with the clear plastic sheets in place. The color of the composites before curing served as the control. RESULTS: Light-curing caused barely perceptible to perceptible color changes for all of the composites from the pre-cured shade. Clearfil and TrueVitality changed color significantly more than Charisma, Conquest C&B and Herculite XRV. Once the composites were light-cured, post-curing caused no further perceptible changes in shade.

Analysis of Variance↗